Official Luthiers Forum!

Ok so I suggested this on another luthier forum and was ripped up but that seems to be a very traditional forum as far as methods go and a member there was nice enough to direct me here. Well my idea involves having a bridge without bridge pins (it'll be the kind where the strings just run in the back of the bridge like breedlove bridges) and then to have a two carbon fiber rods attached to the bridge instead of any traditional bracing. The rods will run on from each end of the bridge to the bottom corner of the sides of the guitar like this:

(I really do apologize for the poor paint rendition but its late and I'm lazy)

My thinking is that the rods will be enough to counteract all the string pull and so the top won't need any bracing although I could be completely wrong of course. People have been worried that it will keep the bridge from moving and so the guitar will sound like poo.

Thanks guys, peace

-Nic

Hi Nic,

It won't sound like poo! It may sound different, but fer cryin' out loud, why can't people allow experimenters to experiment! It might be quiet, it might not have much sustain, but it might sound sweet. Some designs beg to be amplified, and are too quiet just acoustically. But you'll never know until you try!

Your design doesn't remove all the string force, either the shear or the torque from the top. At least, I don't think so. Seems the string pull would still press down on the top. If the CF rods are beefy enough, it would handle much of it, but the tailblock and rims would have to be a bit stronger than usual to handle the torque.

Have you seen the "Bridge Doctor"?

Also, some would argue that a top with no braces at all may not be the Holy Grail. Their mass modifies/carries/accentuates some frequencies, and they may assist the bridge in distributing the string energy across the whole top, quickly.

I say, knock one out and record some sound samples. The more ideas that get tried and reported on honestly the better, and that will lead to new developments. For example, maybe this engineering will make a killer slide guitar.

Dennis

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Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

my only suggestion would be to buy a china made plywood boat oar of a guitar at garage sale and take the fingerboard and top off and try it. youve got nothing to lose and everything to learn. we all could benefit from your results, good - bad or indifferent. what a world it would be if a mans hands could not mold what his mind can dream.

Nic: Think this the kind of question your not going to find an answer to unless you follow the other's recomendation.Experimentation should be encouraged,having said that,think you have created a very strong triangle where the bridge is located etc etc. Not sure how meny builds you have under your belt,if you feel comfortable with the mechanics of building go for it. Building a guitar is a relatively easy project,building a stunning guitar both in looks and tone is very much harder.Good Luck. Tom.

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A person who has never made a mistake has never made anything!!!

The only thing I see with your design, as someone might have mentioned is, the top will be powered more like an archtop , with the string pressure pushing the top towards the back of the guitar , rather than with a standard flat top configuration where the string energy is transfered by the strings torqueing the bridge forward , and pulling up on the top plate . Jody

What are you trying to achieve here? If you restrict the bridge from moving then you are going to change the way it sounds. You don't want to keep the bridge from moving. You would be better served spending your time learning how to tune your top and understanding how it works first. Then you would have an understanding of if this is a good or bad idea. Your idea might be alright for a hollow body electric. But personally I think it's a bad idea. The top and bracing and weights and flex and all that stuff is pretty complex. Perhaps you should purchase the Responsive Guitar and read up on this first. People have been doing this for quite a while. You need to to learn to walk before running. I don't want to discourage you from thinking out of the box but you need to learn why things are what they are first.
Edit: Please don't take this as a rip either.

This is not a rip .. but here is where your design lacks as far as I can tell ...

The rods/bars will be in tension, and thus will rely solely on the glue to hold them into their places. I have not tried to see what the shear force of epoxy is. At teh tail blcok you could always pin the rod.

There is nothing stopping the bridge from rotating forward and down, which all steel string bridges tend to do.

What is there to stop the neck and its string tension forcing the FB ext down onto the top from collapsing ? You NEED something there for sure, whether its a UTB or some CF buttresses.

Like the others have said, its an idea,and you wont know till you try it, but you need to consider the two points above for sure or the top will collapse IMO.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Interesting. My initial thought was that it might impair movement of the top, which probably wouldn't be what you are after. However, no one really knows what the result is for sure until someone tries it. If you do, let us know what you find.

Hi Nic,

I guess I agree with Chris Paulick - it helps to first know the rules, before trying to break them. This will help to understand why changes worked, or didn't work... and some of the more experienced builders here gave you already some advice as to why your idea might not work.

Having said that - if you're interested in alternative approaches, you could check out the bracing and tailpiece system of http://www.batsonguitars.com/. It's certainly something very different form the "typical" X-brace steel-string guitar. Is it better?

Christian

Hey - interesting idea. I'm probably the least experienced to comment yet - so take my reaction for what it's worth. In the traditional structure, the tension of the strings on the saddle transmits the energy from plucking the strings to the soundboard, which then vibrates and "amplifies" the sound, right? (engineers, please correct me if I stray). The challenge is to construct a top which is just structurally strong enough to keep the guitar from folding up under the string tension, but light enough to enable the response you want.
In your design, it looks to me like those carbon rods would impede the vibration of the top - hence preventing response. They'd support the bridge, but do it by affixing it to the tail block. Wouldn't that likely make it very quiet? What am I missing?

Once again, what are you trying to achieve ? Do you want a pinless bridge and are worried about it coming off? It doesn't look like you are after improving the tone too me. I mean what's the goal here? I think there is a better way of doing what ever your after without possibly destroying the tone and making it sound like it's over built. The CF rods won't make any difference with getting rid of braces.

It's funny you would mention Breedlove. Your drawing isn't alot different than the "JLD Bridge Doctor" used by Breedlove. They don't use any carbon fiber though, and there's still some traditional bracing. Try it and see how it works, that's how inovations are made.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Chris, I think the idea was to let the carbon rods absorb all the string tension, so the top can be built as light as possible, which - very generally speaking - would then result in a more responsive top.

A - again generally speaking - worthy goal ...whether this particular idea is suitable or not, I'll let other, more qualified builders comment on...

Christian

Wow thanks for all the feedback, I'm amazed. Lemmie try'n answer some questions I guess. Christian your completely right about my goal. I want to let the top be as light as possible but still strong. For anyone who thinks that my braces will hamper vibrations, thats my main concern as well but then I played an interesting guitar at my local guitar center. It was a breedlove and it sounded great but the interesting thing was that it had a sound port and inside I could see their bridgedoctor-like support system. Here' a pic of what I saw and of what woody was hittin at



It seems to me (correct me if I'm way off) that this would limit movement about as much as my design.

Christian: I really like batson guitars and have studied them carefully. I don't know how good their braces are but they certainly have interesting ideas.

Tony: I hadn't though about the bridge tipping and now I'm concerned about that but I had the same concern as you about body collapse. I had already decided to put the same A style braces leading from the top of where the neck meets the body right under the fb to the sides to hopefully counteract this. Maybe a support more like the breedlove design would better counteract the bridge tipping problem but thats just a thought.

Mark: I think I will for sure tryn do some testing before going all out on this guitar.

Dennis: Thanks I actually hadn't thought about any plus sides to bracing, I had kinda just seen it as unneeded extra weight.

I'm actually thinkin of making a baratone ukulele and us this brace system just as a test run, think that'll work.

Once again thanks guys, this forum rocks

I think the most noticeable acoustic effect of your plan is that you will seriously restrict the movement of the top in the monopole mode. That's where the top pumps in and out like a speaker cone. IIRC, that's also the lowest vibrational mode of the top (pitch that is) so you will probably have weaker sounding basses.

I've heard this artifact (or at least what I think is that artifact) on the banduras that I've built in the past. It is a tailpiece type instrument and I had to put a little support in one part of the bridge. You can really hear the fundamental of the note you're playing get quieter the closer you get (physically) to that support.

edit in bold.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

It limits the movement you want to limit (rotation) more than your design and limits the movement you don't want to limit (up/down) a lot less. Their design didn't come about by chance; they made it that way to resist only the rotation, while having the structure be loose vertically.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

What Bob said: the design as shown would limit the 'loudspeaker-like' movement of the top far more than the JLD system does, and the torquewise movement a bit less. Of course, the devil is in the details; in this case, things like changes in the angles of the braces would make a lot of difference, at least potentially.

I've seen a lot of different schemes over the years to take the torque off the bridge and allow for a lighter top. If they DO take the torque off, and DO end up with a lighter top, I've never been too impressed by the sound. As has been said, it really does seem as though the 'standard' bracing works well in producing a 'guitarlike' sound.

I spent 'way too much time a few years ago looking at the forces the string puts on the top of the saddle. In part, I was trying to settle the 'torque vs up-and-down' question. Basically, from what I can see, in most cases, the 'up-and-down' 'loudspeaker' movement of the top driven by the transverse force has torque beat almost every time, and usually by a lot. I don't know who started the torque-as-driver notion (although I have suspicions), but as far as I'm concerned it's NOT the main driver.

None of this is to try to discourage you from running the experiment. After all, there's a lot we don't know about these boxes, and even if it doesn't work the way you want it to, you'll probably learn something. The only thing I ask is that when you do, you tell the rest of us what you learned. The history of the guitar is littered with unsuccessful experiments that their embarrassed makers buried, and this dooms the rest of us to try the same old things all over again.

My thinking is that much of the "bracing" we put up under there is to keep the top from buckling under the compression forces between the bridge and neck.... This is the concern about the area in front of the bridge dipping... that the Top is buckling rather than torque causing problems.

Think of a Coke can... You can stand on an empty coke can... so long as you don't compromise the integrity of the sides. As soon as you dent a side, the whole thing collapses.

So.... in this context -- I guess I will ask the same question as everyone else here already did..... What does your bracing system do to prevent the bridge from pulling forward and the top buckling?

I hope all goes well with your build

John